VOLTAGE_CURSOR_ADAPTER

Published:2009/7/20 4:08:00 Author:Jessie | From:SeekIC

This is the schematic diagram for the voltage cursor adapter. The required 15- to 25-V power to the circuit can be supplied either by batteries or by a wall-mounted ac to 15-Vdc adapter. The MC78L12 voltage regulator (IC1) supplies regulated 12 Vdc to the rest of the circuit. The ICM7555 timer (IC2) drives the CD4066B, a CMOS bilateral switch (IC3). This drive frequency can either be a normal frequency (NORM) of 100 kHz or a low frequency (LO-F) of 10 kHz, depending on the setting of switch S1. Set S1 to LO-F for inputs below 500 Hz. The dc reference voltage supplied to pin 3 of IC3 is set by R3, a 10-turn, 5000-Ω precision potentiometer. The voltage can be read directly from a turns counter dial coupled directly to the potentiometer's wiper. The accuracy of this reading can be 1 per-cent or better. Trimmer potentiometer R1 permits the voltage to R3 to be calibrated to precisely 10 V. The circuit is calibrated by setting the digital reading on the turns counter of R3 to the full clockwise position and adjusting R1 for a reading of 10 V at the wiper of R3 with a digital voltmeter. Bilateral switch IC3 converts the dc reference to a square wave with exactly the same wiper amplitude. The square-wave output appears on the common pins 4, 9, and 10 of IC3 aqd coaxial plug PL1.



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